JP2006212489A - Grinding method using medium stirring type grinder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a grinding method for grinding a solid material into a nanometer size using a medium stirring type grinder. <P>SOLUTION: The medium stirring type grinder is an apparatus of a type constituted so that a hollow part is formed to a stirring shaft to be opened to the inside of a container in the vicinity of the other end of the container, a grinding medium return passage for allowing the hollow part to communicate with the space between the stirring shaft and the inner surface of the container is formed, the grinding media reaching the vicinity of the other end of the container accompanied by the movement of a slurry enter the hollow part of the stirring shaft from a slurry inlet to be subjected to the circulating motion returning to the space between the stirring shaft and the inner surface of the container from the grinding medium return passage, a slurry outlet is formed to the hollow part and a screen is provided so as to surround the slurry outlet and rotationally driven. The size of the grinding media is set to 20-200 μm and the stirring shaft is driven at a peripheral velocity of 3-8 m/sec. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pulverization method in which a solid is pulverized into fine particles using a medium stirring pulverizer. In particular, the present invention uses a medium stirring type pulverizer such as a sand mill or a bead mill to make minerals, pigments, dyes, chemicals, magnetic materials such as ferrite, ceramics, etc., ultrafine particles, particularly nanometer size. To a method such as coating, printing ink, pigment, magnetic tape coating material, rubber, adhesives, cosmetics, and pharmaceuticals such as paints.

Conventionally, a crusher used for this purpose has a stirrer shaft rotatably disposed in an axial direction in a cylindrical container, and a stirrer such as a stirrer pin is attached to the stirrer shaft so as to project radially. It has a structure. The slurry inlet is provided at one axial end of the container, and the slurry outlet is provided at the other axial end of the container. In the container, a grinding chamber, which is a space between the inner surface of the container and the stirring shaft, is filled with a grinding medium such as zirconia, silica, glass beads, resin, and the stirring shaft is introduced while introducing the slurry from the slurry inlet. The stirring member is rotated to rotate, and the slurry is passed between the pulverizing media, whereby the solid matter in the slurry is finely pulverized or finely dispersed to a desired size. Separating means such as a screen is provided at the slurry outlet in order to separate the grinding medium from the slurry.
In this type of conventional pulverizing apparatus, the pulverizing medium tends to concentrate in a part of the pulverizing chamber, that is, in the vicinity of the slurry outlet, so that a number of problems have been experienced. In order to cope with this problem, Japanese Patent No. 3400087 has a hollow structure in which the stirring shaft is opened at the end portion on the slurry outlet side, and the opening at the end portion functions as an inlet for medium circulation to the hollow portion of the stirring shaft. Then, a slit is formed on the side of the agitation shaft to function as a medium circulation outlet, and the pulverization medium that has reached the vicinity of the slurry outlet in the pulverization chamber is fed from the medium circulation inlet formed at the end of the agitation shaft. A structure is disclosed in which a circular motion is entered into the hollow interior of the medium and returned to the grinding chamber from the outlet for circulating the medium. Japanese Patent No. 3246973 discloses a continuous pulverization system using a medium stirring pulverizer.

  Japanese Patent Publication No. 2-10699 discloses a pulverizing apparatus having a hollow stirring shaft, in which a slurry take-out tube is fixedly disposed inside the hollow of the stirring shaft, and a separation device is provided at the slurry inlet of the tube. The structure provided with is disclosed.

Japanese Patent No. 3400087 Japanese Patent No. 3246973 Japanese Patent Publication No. 2-10699 International Publication WO96 / 39251 (Unpublished prior application) Japanese Patent Application No. 2004-222138 Journal of Powder Engineering, Vol. 41, No. 8 (Vol. 423), pages 16 to 23, issued on August 10, 2004 Proceedings of the 40th Summer Symposium of Powder Engineering Society, July 29-30, 2004, page 13-14, Technical Lecture 5 “Dispersion of Aggregated Nanoparticles in Bead Mill for Microbeads”

The conventional structures disclosed in the above-mentioned Patent Documents 1 to 3 achieve the desired effect for each purpose, but satisfactorily cope with the demands under recent nanotechnology. Is difficult. Specifically, in order to atomize the solids in the slurry to a nanometer size and achieve the atomization within a sufficiently short time, it is necessary to reduce the diameter of the grinding media. It is. The diameter of the beads used in the conventional crushing apparatus is 0.3 mm to 0.5 mm even for extremely small ones used for ultra-fine crushing. Grinding to a grain cannot be achieved satisfactorily. In fact, a bead diameter of 0.2 mm or less is required when dealing with nanotechnology.
In order to pulverize nanometer size, it is attempted to add a dispersing agent such as polycarboxylic acid sodium salt in order to prevent the pulverized particles from aggregating again to a large particle size. . However, in the conventional method, it is necessary to add a large amount of a dispersant in order to achieve a desired pulverization effect, and there is a concern about an adverse effect due to the dispersant. Furthermore, in the conventional method, it takes a lot of time to refine the particles to a desired level, the power consumption is large and uneconomical, and the slurry temperature becomes high, so that the pulverizing medium and the stirring member There is a problem of accelerating wear.

The structure used as the separation device in the conventional pulverizer includes a gap or slit structure and a screen structure. Among these, in the gap or slit structure, it is very difficult to separate the above-mentioned fine diameter beads from the slurry. The screen structure separation device can separate the fine-diameter beads by making the screen finer, but the viscosity increases when the viscosity of the slurry is high or when grinding or dispersion progresses. In the case of slurry, as described above, the pulverized medium having a small size is concentrated in the vicinity of the screen, which causes problems such as abnormal heat generation, abnormal wear, and clogging of the screen.
In addition, in the case of a slurry whose properties change due to heat, in order to suppress a rise in the temperature of the slurry in the pulverizer, the amount of slurry flowing in is increased to suppress the residence time in the pulverizer. In this case, the above-mentioned problem occurs.
Non-Patent Documents 1 and 2 disclose a medium agitation type pulverizer that can use 0.03 mm-sized beads by separating the pulverization medium and the slurry using centrifugal force. And in these documents, by using a pulverizing medium of such a small size and setting the rotation speed of the stirring member within a specific range, reaggregation of pulverized or dispersed particles is prevented, and It has been reported that a good grinding effect could be achieved. In these documents, it is stated that the best pulverization effect can be achieved at the rotor peripheral speed, that is, the stirring member peripheral speed of 10 m / s when pulverization is performed using beads of 0.03 mm size in this apparatus.
In these Non-Patent Documents 1 and 2, a centrifugal separator for separating the pulverization medium and the slurry using the action of the centrifugal force is rotationally driven together with the stirring member, and the pulverization medium is separated from the screen surface by the centrifugal force. It will be understood that even with very small pulverizing media, such as 0.03 mm, it can be separated from the slurry with the effect. Patent Document 4 is a patent application regarding the crushing apparatus mentioned in Non-Patent Documents 1 and 2. As described in Patent Document 4, the centrifugal separator in the pulverizer is composed of a pair of disks and a plurality of blades arranged between the disks.
However, since the centrifuges disclosed in these non-patent documents and Patent Document 4 are mainly separated from the grinding medium and the slurry, the grinding efficiency must be ignored. Further, in this pulverizing apparatus, it is inevitable that the pulverizing medium is concentrated near the slurry outlet of the container. Therefore, although this type of apparatus can achieve a certain level of effect at the laboratory stage, it is not practical for practical machines that require continuous operation over a long period of time.

The present applicant pays attention to many problems in the conventional medium agitation type pulverizers, and in order to solve these problems, a powder that can stably use a pulverized medium having a small diameter (unpublished) Prior application)). As a result of further research using the pulverization apparatus according to this unpublished prior application, the present applicant has completed a method capable of effectively achieving nanometer-sized ultrafine particle pulverization.
That is, the subject of this invention is providing the grinding | pulverization method which can perform nanometer-sized ultrafine grinding | pulverization effectively using the medium stirring type grinding | pulverization apparatus which concerns on the said unpublished prior application. Here, the term “pulverization” is not limited to pulverization in a general sense, but also includes the refinement of particles, sometimes referred to as “dispersion” in the industry, to make the particles finer to a very fine size. Use.

  The medium agitation type pulverizer used in the method of the present invention comprises a cylindrical container having a slurry inlet at one end, a rotatable agitation shaft disposed in the longitudinal direction in the container, and the agitation shaft. And a driving device for rotationally driving. The stirring shaft may have a stirring member, and a grinding medium is placed in a grinding chamber formed by a space between the stirring shaft and the inner surface of the container, and the slurry is driven while the stirring shaft is rotationally driven by a driving device. -By introducing slurry from the inlet, solids in the slurry are crushed. The stirring shaft is formed with a hollow portion opened to the container in the vicinity of the other end of the container, and the stirring shaft has a grinding medium return passage for communicating the hollow portion with the space between the stirring shaft and the inner surface of the container. The pulverization medium formed and reaches the vicinity of the other end of the container with the movement of the slurry enters the hollow portion of the stirring shaft through the opening of the stirring shaft, and passes between the stirring shaft and the inner surface of the container from the grinding medium return passage. Circulate back to the grinding chamber. A slurry outlet is disposed in the hollow portion of the stirring shaft, a screen is provided in the hollow portion so as to surround the slurry outlet, and the screen is rotationally driven.

In this apparatus, the slurry outlet can be formed on the stirring shaft, and the screen can be fixed to the stirring shaft and driven to rotate together with the stirring shaft. A slurry outlet passage leading to the slurry outlet can be provided in the stirring shaft. Alternatively, as another aspect, the slurry outlet is constituted by a tubular slurry outlet member rotatably disposed in the hollow portion of the stirring shaft, the screen is fixed to the tubular member, and the tubular member is rotated separately from the stirring shaft. Means for driving can be provided.
The method of the present invention uses the pulverizing apparatus having the above-described configuration, and the pulverizing medium has a size of 20 to 200 μm, and the stirring shaft is driven so that its peripheral speed is 3 to 8 m / sec. Is. The size of the screen mesh is preferably 1/2 or less of the diameter of the grinding medium, and more preferably 1/3 of the diameter of the grinding medium.

(Function)
According to the above-described configuration of the present invention, the screen for separating the pulverizing medium from the slurry is rotationally driven. Therefore, the rotational motion is induced in the slurry and the pulverizing medium that have reached the vicinity of the screen. The centrifugal force is higher in the grinding medium than in the slurry, and therefore, the urging force away from the screen is generated in the grinding medium. For this reason, the grinding medium circulates without approaching the screen. In the method of the present invention, it is effective to reduce the peripheral speed of the rotational drive of the stirring member to prevent the reaggregation of particles, the power loss is small, and a relatively small input power is 0.1 μm. Crushing to the following sizes is possible. If the size of the grinding medium is 20 μm or less, it is effective for grinding into ultrafine particles, but separation of the grinding medium from the slurry becomes difficult, which is not practical. When the size of the grinding medium is larger than 200 μm, a sufficient grinding effect cannot be achieved.
In the present invention, since a slurry outlet is formed in the hollow portion of the stirring shaft, a screen is provided so as to surround the slurry outlet, and the screen is rotationally driven. Even when a pulverizing medium having a minute size of 2 mm or less is used, the pulverizing medium can be separated from the slurry. Furthermore, it was confirmed that the separation of the grinding media can be achieved without any trouble even if the peripheral speed of the stirring shaft is relatively low. As a result of the study by the present inventors, it has been found that when this apparatus is used, the lower the peripheral speed of the stirring shaft, the lower the input power, and the finer particles can be pulverized. When the peripheral speed of the stirring shaft is 8 m / sec or more, for example, 10 m / sec, it is difficult to pulverize to a particle size of 0.1 μm or less even if the input power is increased. When the peripheral speed is 3 m / sec or less, it may be difficult to separate the slurry and the grinding medium. Here, the peripheral speed of the stirring shaft is the peripheral speed at the distal end in the radial direction of the stirring member when the stirring member is provided on the stirring shaft.
In the method of the present invention, since the stirring shaft is rotated at a low speed, the centrifugal force acting on the grinding medium is relatively low, and the grinding medium is not caused to collide with the inner wall surface of the container by the centrifugal force. Slurry contamination due to media wear is reduced. Further, since the grinding medium circulates from the grinding chamber in the container through the hollow portion of the stirring shaft and returns from the grinding medium return passage to the grinding chamber, contact and collision between the grinding media are reduced, and the grinding media is worn out. And damage is reduced. As a result, the lifetime of the grinding device itself is also greatly increased.
In the present invention, the rotational driving force applied to the stirring shaft and the kinetic energy applied to the grinding medium can be set to values as low as required to disperse the aggregates of particles. And can be pulverized to fine particle size with low power.
In the method of the present invention, the medium agitation type pulverizer is arranged in a circulation system as described in FIG. 1 of Patent Document 2, and the slurry is repeatedly passed through the pulverizer to enhance the pulverization effect. it can.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1A and 1B are a longitudinal sectional view and a transverse sectional view showing a first embodiment of the present invention. As shown in the figure, the pulverizer 1 includes a cylindrical container 2, and a lid member 3 and a bottom member 4 are attached to the liquid nail at both ends of the container 2. Inside the container 2, a rotatable stirring shaft 6 is disposed so as to extend in the axial direction, and a space, that is, a grinding chamber 5 is formed between the stirring shaft 6 and the inner surface of the container 2. The grinding chamber 5 is filled with grinding media such as glass beads and ceramic beads. The grinding media is 20-200 μm in diameter for nanometer size grinding.

  A plurality of rod-like stirring members 7 are fixed to the stirring shaft 6 so as to protrude radially outward with an interval in the axial direction and the circumferential direction. The stirring member 7 may have a disk shape instead of a rod shape. In the case of a disk shape, a plurality of stirring members 7 are fixed to the stirring shaft 6 with an interval in the axial direction.

  A slurry inlet pipe 11 is fixed near one end of the container 2 adjacent to the lid member 3 in the axial direction to form a slurry inlet. The stirring shaft 6 has a shaft portion that passes through the lid member 3 and extends to the outside of the container 2, and this shaft portion is rotatable with respect to the container 2 by the support member 8 but supported so as not to move in the axial direction. Is done. The drive device for rotationally driving the stirring shaft 6 is an electric motor (not shown) or other suitable prime mover. A pulley 10 is attached to the above-described shaft portion of the stirring shaft 6, and the pulley 10 is connected to a pulley (not shown) provided on the output shaft of the prime mover by a transmission belt 9. By this connection, the stirring shaft 6 is rotationally driven by a prime mover such as an electric motor.

The stirring shaft 6 has a cup-shaped hollow shape in which an end portion of the container 2 far from the slurry inlet pipe 11 is opened as indicated by reference numeral 15, and the stirring shaft 6 is a wall portion corresponding to the hollow portion 12. A slit 16 is formed in the upper surface. The opening 15 at the end of the stirring shaft 6 constitutes an inlet for circulating the grinding medium, and the slit 16 constitutes a return passage 17 for circulating the grinding medium.
In the hollow portion 12 of the stirring shaft 6, a slurry outlet pipe 18 that extends through the stirring shaft 6 and into the hollow portion 12 is disposed. The end of the slurry outlet pipe 18 is located in the hollow portion 12 of the stirring shaft 6 and constitutes the slurry outlet 13. The slurry outlet pipe 18 communicates with the slurry outlet 13 and constitutes a slurry outlet passage that passes through the stirring shaft 6 in the axial direction.
A screen 14 is arranged in the hollow portion 12 of the stirring shaft 6 so as to surround the slurry outlet 13. The screen 14 is fixed to the stirring shaft 6 and rotates together with the stirring shaft 6.
In operation, a slurry containing solid matter to be pulverized, for example, calcium carbonate slurry, is continuously driven to rotate at a predetermined flow rate by a slurry pump (not shown) while the stirring shaft 6 is rotationally driven. Are introduced continuously. Since the operation of the medium agitation type pulverizer is well known, detailed description thereof is omitted.

  In the vicinity of the end of the crushing chamber 5 far from the slurry inlet pipe 11, the slurry and the crushing medium are used for circulating the crushing medium formed by the opening 15 at the end of the stirring shaft 6, as indicated by an arrow 20. The slurry enters the hollow portion 12 of the stirring shaft 6 from the inlet, passes through the screen 14, and is taken out from the slurry outlet 13 through the slurry outlet pipe 18. Since the pulverizing medium is urged radially outward by the action of centrifugal force accompanying the rotation of the screen 14, the pulverizing medium is separated from the screen 14 and passed through the pulverizing medium circulation outlet 17 formed by the slit 16 to the pulverizing chamber 5. Returned. Therefore, when the grinding medium has a small diameter, there is no possibility that the grinding medium clogs the screen 14. As a result, abnormal wear of the screen is prevented and the problem of abnormal heat generation does not occur.

FIG. 2 is a longitudinal sectional view showing another embodiment of the present invention. In this embodiment, the parts corresponding to the embodiment of FIG. 1 are shown with the same reference numerals as those of FIG.
In this embodiment, the slurry outlet pipe 18 is formed separately from the stirring shaft 6.
One end portion of the slurry outlet pipe 18 is located in the hollow portion 12 of the stirring shaft 6 and constitutes the slurry outlet 13. The screen 14 surrounding the slurry outlet 13 has a rotating shaft that extends through the bottom member 4 in the axial direction and extends outside the container 2, and this rotating shaft is rotatable with respect to the bottom member 4 by the support member 21. Is supported so as not to move in the axial direction. A pulley 23 is fixed to the outer end of the rotating shaft of the screen 14, and this rotating shaft is rotationally driven by a driving device such as an electric motor (not shown) via a transmission belt 22 wound around the pulley 23. The operation of this embodiment is the same as that of the embodiment of FIG.
3 to 6 are cross-sectional views showing various shapes of the stirring member 7. FIG. 3 shows an example of a disc-shaped stirring member. 4 shows an example of a fan-shaped stirring member, FIG. 5 shows a triangular stirring member, and FIG. 6 shows an example of a cylindrical stirring member. In the example of FIG. 6, a cylindrical protrusion is formed on the outer surface of the stirring shaft, and a slit 16 is formed through the protrusion.
FIG. 7 is a schematic view showing an example apparatus in which the medium stirring type pulverizer is used as a circulation system. The slurry outlet pipe 18 of the pulverizer 1 shown in FIG. 1 is connected to the upper part of the slurry tank 26 by a pipe line 24. The bottom of the slurry tank 26 is connected to the slurry inlet 11 of the pulverizer 1 by a pipe line 27 having a slurry pump 25. The slurry tank 26 is provided with a stirring blade 29 that is rotationally driven by an electric motor 28. Such a circulation system is described in Patent Document 2.

In the present invention, the diameter of the grinding medium is 20 to 200 μm as described above, and the stirring shaft 6 is rotationally driven so that its peripheral speed is 3 to 8 m / sec. Here, when the stirring member 7 is provided on the stirring shaft 6, the peripheral speed of the stirring shaft 6 is the rotational speed at the tip of the stirring member 7.
(Example)
By the method of the present invention, crystal structure anatase type titanium oxide for photocatalyst was pulverized, ie, dispersed. The slurry was adjusted so that water was used as a solvent and the solid content concentration was 5%. A synthetic polycarboxylic acid sodium salt marketed under the name Aron T40 by Toa Gosei Co., Ltd. was added as a dispersant in a proportion of 5% by weight with respect to titanium oxide. The medium agitation type pulverizer having the structure shown in FIG. 1 was used, and a slurry tank provided with agitation blades 29 was arranged as shown in FIG. The amount of slurry supplied was 180 kg / h. Zirconia spheres were used as the grinding media, and grinding was performed when the grinding media had a diameter of 300 μm, 200 μm, and 100 μm. The peripheral speed of the stirring shaft was 4 m / sec. The obtained results are shown in FIG. 8 in relation to the particle diameter after pulverization and the input power. The particle size of the particles was measured using a Microtrac particle size distribution measuring device manufactured by Nikkiso Co., Ltd.
In the same pulverizer, the slurry adjusted as described above using a pulverizing medium of 200 μm zirconia spheres was pulverized. The peripheral speed of the stirring shaft in this case was 13 m / sec, 10 m / sec, 8 m / sec, 6 m / sec, 4 m / sec. The obtained result is shown in FIG.
As can be seen from FIG. 8, when the diameter of the grinding medium is 300 μm at a stirring shaft peripheral speed of 4 m / sec, it is difficult to perform grinding of 0.1 μm or less even if the input power is increased. As can be seen from FIG. 9, when a grinding medium having a diameter of 200 μm is used, it cannot be ground into fine particles of 0.1 μm or less unless the peripheral speed of the stirring shaft is 8 m / sec or less. This is presumed to be a result of the particles once pulverized being re-aggregated by the applied energy. Furthermore, it can be seen that the smaller the grinding medium diameter and the lower the peripheral speed of the stirring shaft, the higher the grinding effect can be achieved with low input power.
FIG. 10 shows a comparison between the particle size distribution of the particles before pulverization and the particle size distribution after pulverization at a stirring shaft peripheral speed of 13 m / sec and 4 m / sec using a pulverization medium having a diameter of 200 μm. From this figure, it can be seen that the effect of reducing the particle size distribution can be achieved by grinding at a peripheral speed of 4 m / sec. On the other hand, at a stirring shaft peripheral speed of 13 m / sec, an undesirable result that the particle size distribution becomes wide is obtained.
FIG. 11 is an X-ray diffraction diagram showing the crystal structure of the particles. As can be seen from the figure, in the pulverization treatment at the stirring shaft peripheral speed of 4 m / sec, there is almost no change in the crystal structure of the particles. On the other hand, it can be seen that at a stirring shaft peripheral speed of 13 m / sec, the crystal structure is broken and amorphous.
(effect)
In the present invention, the stirring shaft is formed with a hollow portion having a grinding medium inlet in the vicinity of the other end of the vessel, and a slit that communicates the hollow portion with the space between the stirring shaft and the inner surface of the vessel. The pulverization medium that reaches the vicinity of the container end with the movement enters the hollow part of the stirring shaft from the slurry inlet and circulates back to the space from the slit, thereby preventing the tendency of the pulverization medium to concentrate on the container end. Is done. Furthermore, according to the present invention, the slurry outlet is disposed in the hollow portion of the stirring shaft, the screen is provided so as to surround the slurry outlet in the hollow portion, and the screen is configured to be rotationally driven. The grinding media heavier than the slurry is urged away from the screen by the action of centrifugal force, and there is no possibility of clogging the screen even if a fine particle size grinding media is used for nanometer size grinding. Therefore, in the present invention, it is possible to use a fine-diameter grinding medium without worrying about clogging of the screen, and it is possible to perform low-energy grinding by reducing the peripheral speed of the stirring shaft. become. For this reason, it becomes possible to perform nanometer-size grinding on an industrial scale without adversely affecting the crystal structure of the particles.

(A) is a longitudinal cross-sectional view of the medium stirring type crushing apparatus which shows one Embodiment of this invention, (B) is a cross-sectional view of the crushing apparatus shown to (A). The longitudinal cross-sectional view of the medium stirring type crusher which shows 2nd embodiment of this invention. The cross-sectional view of the crushing apparatus which shows the example of a disk shaped stirring member. The cross-sectional view of the crushing apparatus which shows the example of a fan-shaped stirring member. The cross-sectional view of the crusher which shows the example of a triangular stirring member. The cross-sectional view of the crushing apparatus which shows the example of a cylindrical stirring member. Schematic which shows the arrangement | positioning which connected the medium stirring type crusher shown in FIG. 1 to the slurry tank, and was set as the circulation system. The chart which shows the result of having grind | pulverized using the grinding medium of several different diameters in the apparatus of FIG. The chart which shows the result of having grind | pulverized by several different stirring shaft peripheral speeds in the apparatus of FIG. The chart which shows the relationship between stirring shaft peripheral speed and particle size distribution. The chart which shows the influence which stirring shaft peripheral speed has on crystal structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Crusher 2 Container 3 Cover member 4 Bottom member 5 Crushing chamber 6 Stirring shaft 7 Stirring member 12 Hollow portion 13 Slurry outlet 14 Screen 15 Medium circulation inlet 16 Slit 17 Medium circulation outlet 18 Slurry outlet pipe

Claims (5)

A cylindrical container having a slurry inlet on one end side, a rotatable stirring shaft disposed in the longitudinal direction in the container, and a drive device for rotationally driving the stirring shaft, the stirring shaft and the A slurry is obtained by filling the grinding chamber between the container with a grinding medium, introducing the slurry from the slurry inlet while rotating the stirring shaft, and discharging the slurry from the slurry outlet connecting the inside of the container to the outside of the container. It is a pulverization method for performing nanometer size pulverization of a solid using a medium stirring type pulverizer adapted to pulverize the solid inside,
As the medium agitation type pulverizer, a hollow portion is formed in the stirring shaft, and the hollow portion is opened in the container in the vicinity of the other end of the container. The stirring shaft and the inner surface of the container are provided in the stirring shaft. A grinding medium return passage communicating with the above-mentioned space between the two and the grinding medium is reached, and the grinding medium reaching the other end of the container as the slurry moves enters the hollow portion of the stirring shaft from the slurry inlet, A circulation movement is made to return to the space between the stirring shaft and the inner surface of the vessel from the grinding medium return passage, a slurry outlet is formed in the hollow portion, and a screen is provided so as to surround the slurry outlet. Using a device of the type in which the screen is driven to rotate,
The size of the grinding medium is 20 to 200 μm,
Driving the stirring shaft so that its peripheral speed is 3-8 m / sec,
A pulverization method characterized by the above.   2. The method according to claim 1, wherein a device of a type in which a stirring member projects outward in the radial direction is used for the stirring shaft.   3. The method according to claim 1 or 2, wherein the grinding medium is filled in an amount of 60 to 90% of an effective volume of the grinding chamber.   The method according to any one of claims 1 to 3, wherein the grinding medium is formed from any one of zirconia, silica, glass, and resin.   The method according to any one of claims 1 to 4, wherein the solid in the slurry is titanium oxide.

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